Make sure to say you want 2048 bits or the router will fall back to ssh 1 and won't allow you to have ssh 2

router(config)#crypto key generate rsa
The name for the keys will be: router.<YOUR DOMAIN>
Choose the size of the key modulus in the range of 360 to 2048 for your
General Purpose Keys. Choosing a key modulus greater than 512 may take
a few minutes.
How many bits in the modulus [512]: 2048
% Generating 2048 bit RSA keys, keys will be non-exportable...
router(config)#ip sh version 2

Besides changing the obvious things such as the hostname, domain name, and permitted IPs, you'll also need to verify the ATM0 settings match your ISP's configuration. Specifically: "pvc 8/35" and "encapsulation aal5snap" works for me but may not for you. You will also need to generate the passwords and replace all the instances of <SECRET>.

Generating the passwords

Secret 5 Password

You can generate the hash for the "secret 5" passwords with this OpenSSL command:

openssl passwd -salt `openssl rand -base64 3` -1 "<YOUR PASSWORD>"

Put the output in <SECRET>

Secret 7 Password

To encrypt the secret 7 password you can use this perl script thanks to m00nie.